Plugin: Hotlink Prevention
Author: Mark Wu
License: Creative Commons Attribution-NonCommercial-ShareAlike 2.5
Lincese URL: http://creativecommons.org/licenses/by-nc-sa/2.5/deed.en
Restriction: CAN'T USE THIS PLUGIN IN COMMERCIAL PURPOSE OR ENVIRONMENT. If you want to use this plugin in commercial purpose or environment, just donate US$ 20 to pLog team or me. I'll grant the permission to you after I got the donation.
Release Date: 2005/09/16
Version: 1.0

This plugin offers the most powerful hotlink prevention for your resource. Usage as follow:

Install:
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1. Install this plugin to your ./plugins folder
2. Site owner can reach the control panel through "Admin Settings >> Global Settings >> Hotlink Prevention"
3. Blog owner can reach the control panel through "Control Center >> Security Management >> Hotlink Prevention"

Hotlink Prevention Algorithm:
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1. Check the request referer. 
    - If the referer is blank, check the "blankrefererenabled" parameter is enable or not.     - If "blankrefererenabled" parameter enabled, go to step 3. if disabled, banned the request. 
    - If the referer is not blank, go to step 2.
2. Check the request referer is available in allow referer list or not. 
    - If yes, return the request content to user. 
    - If not, go to step 3.
3. Check the file extension is protected or not. 
    - If yes, banned the request.
    - If not, return the request content to user.

Notice:
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If you found this plugin is useful, please kindly make donation to pLog project or myself (Mark).